I've tried it over the last few days. My advice would be to wait for the version 2 xml file he will release shortly. The current version has broken light sources at night (lamp posts and other lights).
I've done a lot of tests and whilst it sounds promising, with the fault above and other stuff, I really can't see any difference between in game ultra settings and this file during the day. At night yes, but that's because the light sources are bust, so it looks different.
He needs to do a proper side by side, like for like comparison video at exact same time of day, because as it stands people are getting excited but there's no real 'proof' that its 'better'.
You will also need to tweak the file to your own settings - like resolution, vsync, all the other gubbins so you need to be comfortable editing a bit of code. It's not hard though really.
Most important thing is to make sure you set the file to READ ONLY after your tweaks other wise it will get overwritten by the game if you make any other minor changes in game.